The present invention relates to a pastable emulsion polymer comprised of carboxylated monomer/vinyl chloride/vinyl acetate terpolymer having improved strength of adhesion produced by emulsion copolymerization and containing, per polymer weight,
from 60% to 98% by weight of vinyl chloride monomer units, PA0 from 1% to 29% by weight of vinyl acetate monomer units, and PA0 from 1% to 15% by weight of carboxyl-containing monomer PA0 from 60% to 98% by weight of vinyl chloride monomer units, PA0 from 1% to 29% by weight of vinyl acetate monomer units, and PA0 from 1% to 15% by weight of carboxyl-containing monomer units selected from the group consisting of olefinically-unsaturated monocarboxylic acids, monoallyl esters of non-ethylenically-unsaturated dicarboxylic acids and monovinyl esters of non-ethylenically-unsaturated dicarboxylic acids.
units selected from the group consisting of olefinically-unsaturated monocarboxylic acids, monoallyl esters of non-ethylenically-unsaturated dicarboxylic acids, and monovinyl esters of non-ethylenically-unsaturated dicarboxylic acids. Preferably the pastable emulsion polymer contains from 78% to 97% by weight of vinyl chloride monomer units and from 2% to 10% by weight of said carboxyl-containing monomer units.
Hereinafter vinyl chloride will sometimes be referred to as VC and vinyl acetate, as VAC.
According to the ivention, olefinically-unsaturated monocarboxylic acids or monoallyl or monovinyl esters of non-ethylenically-unsaturated dicarboxylic acids are used as monomers containing carboxyl groups.
The emulsion polymer according to the invention can be processed, preferably in a manner known per se, to form plastisols, vinyl chloride pastes, and dispersions of pulverulent pastable PVC or of vinyl chloride copolymers in suitable plasticizers.
Pastable VC/VAC/maleic anhydride terpolymers, for example, have been described in DE-AS No. 16 45 672 and DE-AS No. 17 45 561, corresponding respectively to U.S. Pat. Nos. 3,632,562 and 3,624,051. Compared with the terpolymers described in those Auslegeschriften, which are applied in the form of a paste to fabrics, the terpolymers according to the invention-even those having a relatively low content of carboxyl groups, surprisingly have improved adhesive strength when used as pastes for coating flexible sheet-like articles, especially of plastics or natural materials, such as, for example, preferably films and woven or non-woven fibre products, such as textiles, fibre fleeces, paper and pasteboard. Moreover, the terpolymers according to the invention can be manufactured in a considerably shorter time with better yields than can the previously known terpolymers.
Terpolymers of vinyl chloride, vinyl acetate and a further, carboxyl group-containing, comonomer, which exhibit improved adhesion to metal, are described in Swiss CH-PS Nos. 316 163 and 273 079 and Belgium BE-PS No. 609 934. Those polymers can, however, because of their molecular structure and their outer form which results from their manufacture in suspension, solution or emulsion with subsequent precipitation by coagulation, be processed only as solutions in organic solvents, for example ketones, carboxylic acid esters and the like. Their use is therefore mainly in the field of lacquers. The coating of flexible sheet-like articles with lacquer solutions of this type is technically complicated and often unsatisfactory. Often it is impossible to use such solutions because the substrate to be coated is sensitive to the solvent, but in any case the solvent vapors present the user with problems concerning environmental pollution and hygenic working conditions, which can be solved only at great expense, if at all. Furthermore, even the unavoidable losses of solvent through evaporation make the use of such lacquers considerably more expensive. If modification of the coating is required, for example by using plasticizers or similar additives, the user is faced with further substantial difficulties.